The present invention relates to a piston system and apparatus for harnessing energy from a pressurized fluid flowing in a pipeline.
Fluids flowing through a pipeline are typically under pressure to provide motive energy to the fluid. A fluid, namely liquid or gas, which is under pressure from natural sources such as oil or natural gas from an underground reservoir or well may be harnessed in whole or part to perform other functions or tasks. At well sites in the oil and gas industry, for instance, energy is often needed to operate instrumentation and pumps for a variety of purposes, including glycol dehydration, methanol injection, heat tracing of liquid lines, chemical injection, and the like.
At remote well sites where delivery of electricity is not feasible from an existing power grid, the associated pumps must be operated by other means. Typically, at natural gas well sites, a portion of the gas from the well""s main gas stream is diverted for running the instrumentation and pumps. A significant drawback of these existing arrangements is that the gas is vented to atmosphere as exhaust after being used in the pumps and instruments. There appeared to be no practical and economical means for recovering such vented gas, particularly since the exhaust is at a significantly lower pressure than that of the gas pipeline. Hence, well site operators are faced with the undesirable results of emitting raw gas to atmosphere, which is believed to be detrimental to the environment, as well as losing the opportunity to sell the vented gas.
A new system and apparatus which overcomes the limitations and problems of the prior pump arrangements was proposed in my U.S. Pat. No. 6,065,387. In the apparatus disclosed in this patent a hollow elongate barrel having a top end, an opposed bottom end with an inlet in fluid communication with an upstream portion of the pipeline, and an outlet located intermediate the top and bottom ends in fluid communication with the pipeline downstream of the upstream portion are provided. A piston is movable upwardly in the barrel by pressurized fluid beneath the piston to an upper limit of travel upon the closure member closing the throughhole and the piston is allowed to fall by the force of gravity from the upper limit of travel to a lower limit of travel upon the closure member opening the throughhole to allow the fluid beneath the piston to travel to the interior cavity and to the outlet of the barrel for discharge into the downstream portion of the pipeline. A piston rod extends from the upper end of the piston and slidably through the top end of the barrel in a relatively fluid tight manner for transferring movement of the piston to the exterior of the barrel. This apparatus represents a fairly simple and compact device with a few moving parts for efficiently and automatically harnessing energy from a pressurized fluid stream in a pipeline to perform a desired task. The system is fully self contained in that any fluid diverted from the main fluid stream is returned to that fluid stream without any venting to atmosphere. The harnessed energy may be transferred elsewhere mechanically, such as by a movable piston rod to perform work such as pumping or compressing other fluids, or by other suitable means such as an electrical transfer. The above described apparatus can however be further improved.
Accordingly, it is an object of the present invention to provide a piston apparatus for gas/liquid pipeline of the above mentioned type, which is a further improvement of the existing apparatus.
In keeping with these objects and with others which will become apparent hereinafter, one feature of present invention resides, briefly stated, in an apparatus which has a hollow elongate barrel having a top end, an opposed bottom end, an inlet in fluid communication with a portion of the pipeline, and an outlet in fluid communication with another portion of the pipeline; a piston located within said barrel for reciprocating sliding therein in a relatively fluid-tight manner, said piston having a through hole for fluid communication between a space above said piston and a space below said piston, and a cyclically operable closure member for opening and closing said through hole, said piston being moved upwardly in said barrel by the pressurized fluid beneath said piston to an upper limit of its travel upon said closure member closing said through hole and being allowed to fall by force of gravity from said upper limit of travel to a lower limit of travel upon said closure member opening said through hole to allow said fluid beneath said piston to travel above said piston for discharge of the fluid into the pipeline, said piston including a piston rod extending from an upper end of said piston through said top end of said barrel in a relatively fluid-tight manner for transferring movement of said piston to an exterior of the barrel, and a lower piston rod extending from a lower end of said piston through said bottom end of said barrel in a relatively fluid-tight manner for transferring movement of said piston to an exterior of said barrel.
When the piston apparatus is designed in accordance with the applicant""s invention, it allows a load to be connected to either or both ends of the apparatus. A further important benefit of connecting a piston rod to each of the upper and lower ends of the piston, is that it allows the device to operate at unlimited pressure. The piston surface exposed to the pressurized fluid on the upper end of the piston is equal to that on the lower end of the piston. When a rod is used only on the upper end, the above mentioned surface areas are not equal, and the undesirable result is that the piston can be held at the upper limit of travel indefinitely, by the greater force on the lower end, due to the greater surface area on the lower end.
Another important improvement lies in the closure member apparatus, which achieves a xe2x80x9csnap actionxe2x80x9d of the valve and full travel of the valve to its limits in both directions. As a result, the situation is eliminated where the valve may open only partially, or close only partially, and the piston xe2x80x9cstallxe2x80x9d in a state of equilibrium.
A third significant improvement is the fact that the valve now enters into the opening, to close off the through hole. This ensures equal area on top and bottom surface of the valve, exposed to the pressurized fluid. A valve which simply covers over the opening, as in the prior art, has the problem of unequal areas exposed to the pressurized fluid, and requires greater total force to open it.
A cost saving improvement is the fact that the cylinder ends are now simply flat surfaces. No cone is required on the underside of the top end, and no bridge is required on the upper side of the bottom end.
Still another improvement is that fluid exits the barrel out the top end, just as it enters through the bottom end. No opening is required through the side wall of the barrel or cylinder.
Finally, the piston no longer has to be a hollow structure. It is simply a solid piece with a hole through it.
The novel features which are considered as characteristic for the present invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.